The changes in the system of financial intermediation encourage banks to develop transactions in securities. However, the possibilities of investing banks' monetary stocks in the securities market are limited. The study focuses on the analysis of factors determining the autonomy of domestic banks in modeling the structure of the securities portfolio.

The bank's securities portfolio strictly correlates with the value of deposits and lending facilities, i.e. it depends on the nature and quality of the traditional banking services. The analysis of the statistical data on the operational activities of the domestic banks for the period 1996-2004 shows no major change in the character of such activities. In paralel, with the growing share of deposits from the non-financial sector in the bank's balance sheet total, the lending exposure also follows a rising tendency. The share of securities in the banking sector balance sheet total stabilises, even though a steady annual net rise in the net portfolio of securities led to a 89% rise in the portfolio value between 2004 and 1996. Changes also affect the structure of the securities portfolio in domestic banks. The study identifies factors which determined the portfolio over the analysed period. Their assessment shows that legal factors resulting from the effective provisions of the banking and securities law were of fundamental importance for the decisions to invest on the securities market taken by domestic banks. External factors also played an important role, in particular those related to the maturity of particular segments of the securities market.